The solar wind particles reflected by the lunar magnetic field are the major energy source of electromagnetic wave activities, such as the 100 s magnetohydrodynamic waves and the 1 Hz whistler-mode waves generated by protons and the non-monochromatic whistler-mode waves generated by mirror-reflected electrons. Kaguya found a new type of whistler-mode waves at 100 km altitude above the polar regions of the moon with a broad frequency range of 1–16 Hz. The waves appear diffuse in both the time and frequency domains, and their occurrence is less sensitive to the magnetic connection to the lunar surface. The polarization is right-handed with respect to the background magnetic field, and the wave number vector is nearly parallel to the magnetic field perpendicular to the solar wind flow. The diffuse waves are thought to be generated by the solar wind ions reflected by the lunar magnetic field through cyclotron resonance. The resonant ions are expected to have a velocity component parallel to the magnetic field larger than the solar wind bulk speed; however, such ions were not always simultaneously detected by Kaguya. The waves may have been generated above the dayside of the moon and then propagated along the magnetic field being convected by the solar wind to reach the polar regions to be detected by Kaguya.

Reversal of unified polarization of low-frequency magnetic field variation was found by Kaguya at equator crossings in the lunar wake under the condition of dawn-dusk directed background magnetic field. The polarization was left-handed over a frequency range from 0.01 to 0.3 Hz in the southern hemisphere of the lunar wake in the dawnward-directed magnetic field. It turned to be right-handed when the spacecraft entered the northern hemisphere of the wake. In the duskward-directed magnetic field the polarization reversed. The same configuration by 90 degrees rotated was observed in northward-directed magnetic field, too. The sense of rotation was alike that of surface waves generated by Kelvin-Helmhlotz instability, but it was not likely because the waves of unified polarization were not always accompanied by velocity shear. They penetrated into the very center of the wake, suggesting that they were not propagating along a surface of wake boundary. The polarization was highly elliptic except for high frequency component. The magnetic field variation was predominantly perpendicular to the background magnetic field, suggesting that they were shear Alfven waves. The mechanism of unifying the polarization is not yet understood.